Such a heat exchanger tube is known, for instance from EP 1 429 085. Said document EP 1 429 085 describes a heat exchanger with a number of parallel tubes. The cross-section of each tube goes from being round close to a first outer end attached to a mounting plate to being elliptical in a central part. From there the cross-section changes again to a round shape at the second outer end, which is likewise attached to a mounting plate. The round cross-sectional shape at the ends is chosen here for a simple mounting in round openings in the plates.